Method of handling heattreated rivets



Patented Aug. 3, 1948 PATENTi C Md a corporation of Maryland l I Wi Anplicationnugusc 2 .31942,

Serial No. 456,204"

mounts. (cum-13) This invention relates to a -m'ethod for the heat treatment of aluminum alloy rivets, particularly the rivets known commercially as A178 and 24S...

: ,The chemical analysis of-24S aluminum alloy, which. is the alloyused most extensively in, air craft productionis as follows; a i w i The analysis of theAl'lS aluminum alloyis as follows: i i i Per cent Aluminum 97.2 Copper 2.5 Magnesium .3

These alloys are but little heavier than aluminum,-and in the soft or annealed state, are only slightly stronger but after suitable heat treatr'nent,- developphysical properties somewhat in excess of low carbon steel. Heat treatment consists of raising to a certain temperature, ametal or alloy, and then rapidly cooling the material, by quenchin-g in water. The time between the heating to the predeterminedtemperature and thequenching operation should be as short as possible. Thematerial in the 24S alloyis soft after quenching but attains 90% of its maximum hardness and strength after aging for 24 hours at room temperature, and full strength after 4 to=6 days. This age hardening is very rapid in the first four hours, for which reason, it

is essential that any bending or forming opera tion be carried out in as short a time as possible after the heat treatment. In no case, should the interval exceed" one hour.

Aluminum alloy rivets have the same characteristics as the material in other forms and should undergo similarheat treatment before use. Unless the 24S rivets, after heat treatment, are stored at very. low temperatures, they must be used within twentyminutes.

The-A178 rivets can be used at anytime; after the initial heat treatment,as they are of a modified chemical analysis,

In the fabrication of aircraft, where. many pounds of these rivets, areused, it is necessary to heat treatquantities of these rivets at a time. Both rivets are heat treated-and dried toprevent corrosion. The A1'7Sare"stored'at 'room ternperature but the 24S rivets must be stored at-very the age hardening described above. i a i L'I-he heat treatment of difieressentially from the heat treatment of other products. There are the two common steps.

of heating and quenching the rivets. The novelty in. this .method forheat treatment of' rivets residesin the quenching andhandlingof the rivets during and after quenching.

Theheat treatment of the above rivets, is carried out by means of a container. oi stainless steel into which the rivets are loaded.

'The loadedcontainer is placed. in a furnace for the requiredtime to ensure satisfactory heat treatment of the rivets. The container is then removed. from the furnace and placed over the. wire quench basket. The quench basket is about the sameisize and capacity as the heating, container, and therivets are dumped into the wire quench basket. The wire quench basket is ina tank of waterat about 32 F. which is kept cooled and rapidly circulated. The'dumping from one container to the, other, protects the containers from injury in the process and tumbles the rivets.

while being quenched which ensures a more rapid and uniform quenching. The time between the removal from the furnace to the quenching should be asshort as possible. i

The heating basket is then returned to the loading table. The quench basket is removed from the water tank and transferred to an al-. cohol bath. ;Whi1e alcohol is used in the pre-.

ferred form, any highly volatile solvent having ahighafiinity forwatermay be used, such as a ketone. For best results, the solvent must have a vapor pres-sure of the same order as ordinary commercial. alcohol, that is, ethyl, methyl and PI'ODYI: alcohols, all of which have vapor pressures greater, than 1 mm. of mercury for the range of tempera'tures involved in the method offithis .inventionr, Ketones such as dimethyl ketone (acetone) and methyl ethyl ketone also have vapor pressures in this range and-aremiscible. with 'water. Solvents which can be satis-, factorily used in this method may also be characterized by havingboiling points of less than C. The alcohol bath is held at about 5 to 15 F. The rivets are removed from the alcohol bath and transferred to smalltubular containers which are placed in cold storage. 3

- The rivet containers are placed in master stor-' age boxes immediately after heat treating. Traveling storage boxes which are also refrigerated 'are provided' to take the rivets from the masterstorage box to station storage boxes from which; they'are secured by the men using the. rivets. lo M these rivets does not While the heat treatment is the same, the A178 rivets need not be stored in refrigerated cabinets but the alcohol bath is necessary to dry the rivets properly, before storage, to prevent corrosion.

The 248 rivets, as above described must be kept at about *-2i) F. The alcohol 'bath does two things, itJremoves water and quickly dries the. rivets, thus preventing corrosion, and it prevents the rivets from freezing in clusters and sticking in the small tubular container in which they are stored at 20 F. E'vaporation'of the water or alcohol after the bath aids in the prevention of detrimental temperature rise; i

It has always been a problem with the 2&8

rivets, to quench, dry and store without havingthe temperature of the rivets rise during the. w

The only near successful expedient process. known up to the time of applicant's invention, is the centrifugal drier. centrifugal drier is that if the rivets are whirled long enough to dry properly so they won't corrode or sticktogether at +20" F., they. will undergo a temperature rise If the whirling tirneis limited so that there will not be an injurious temperature rise, it will not besufiicient to dry the rivets, and they will corrode and freeze together in the containers.

It will be noted in applicant's invention that from the quench tank (32 F.) to t e alcohol bath (5 to 15 F.) to the cold storage cabinets (-20 FJ-th-e time-temperature relationship is continuously downward. It will also be noted that the alcohol bath insures removal of the water so the rivets will not corrode or freeze together. in the container at -20 F.

Rivets treated by applicant's method will not shear off or develop cracks or otherwise fail after aging.- i

It is to be understood that eertainohanges, alterations, modifications and substitutions can be made without departing from the spirit and scope of-the appended claims.

I claim as my invention: a l

-1. The method of treating age-hardening aluminum alloy rivets, the hardening of whch may be arrested by refrigeration, which comprises heatmg the rivets, quenching said rivets in cold water, at about 32 F. rinsing said rivets in an alcohol bathkept at a lower temperature than the water, and storing said rivets in refrigerated storage cabinets. I I

2. The method of treating age-hardening alum-- inum alloy rivets, the hardening of which may be arrested by refrigeration, which comprises heating the rivets, quenchingsaid rivets in water; at about 32 F. rinsing said rivets in a bath of a liquid having a boiling point below 90 C. and miscible with water kept at a lower temperature than the water and storing said rivets in refrigerated storage'cabinets'. r

3. The method of treating age-hardening aluminum alloy rivets, the hardening of which may arrested by refrigeration, which comprises the: steps of heating, quenching in water at about 32 F., rinsing in alcohol, and storing in refrigerated cabinets, the temperature of the rivets-being positively reduced ateach step.

4. The method of treating age-hardening aluminum. alloy rivets, the hardening; of which may be arrested by refrigeration, which comprises the: steps of: heating, quenching in water at about 329?. rinsing in a liquid having a boilingv point below 909 C, and miscible with water, and storing in retrigerated cabinets,.the temperature: of the rivets being positively reduced at each step;-

step undergoing a reduction of temperature.

. 6,, The method of treating age-hardening alumalioy'rivets, the hardening of which may be arrested by refrigeration, preparatory to storage in refrigeratedcabinets, which comprises the steps of heating said rivets, quenching in water at about 32 F. displacing the water from said rivets by a liquid havinga boiling point below 90 C. and

, miscible with water, the temperature of the The difliculty with the rlvetsbeing continuously reduced at each step.

7. The method of treating age-hardening aluminum alloy rivets, the hardening of which may be arrested by refrigeration, which comprises heating the rivets, quenching said rivets in water at about 32 Fl, rinsing said rivets in a bath of a liquid having a boiling point below C. and miscible with water, said bath being kept at 5 to 15 F., and storing said ri vets in refrigerated storage cabinets at about -20 F. until used.

8,. The method of treating age-hardening aluminum alloy parts in bulk, the hardening of which may be arrested by refrigeration, which comprises heating the parts, quenching said parts in water at about 32 rinsing said parts in a bath of a liquid havinga boiling point below 90 C; and miscible with Water, said bath being maintainedat 5 to 15 F, and storing said rivets in refrigerated storage cabinets at about -20 F. untilused. 9. The method of treating age-hardening aluminum alloy parts, the hardening of which may be arrested by refrigeration, which comprises heating said parts, quenching said: parts in ,water' at,about 3-2 rinsing. said parts in a loath of a liquid having a boiling point below 90 C. and miscible with water, said bath beingmainta-ined at a lower temperature than the waterand stor ingsaid parts in refrigerated storage cabinets the temperature of said parts being positively reaimed at each step; y y 10.-The method of treating age-hardening. aluminum alloy rivets, the hardening of which may be arrested-by refrigeration, which comprises subjecting the rivets to a solution heat treatment, quenching'said rivets in water maintained at not more than, about room temperature, rinsing saidrivets in alcohol the temperature of which is lessthan the freezing point of water, and then star--- ing the rivets in refrigeration cabinets maintained at a temperature below 20- F..

JOHN HENRY EAIDES.

REFERENCES CITED The following references are of record 'in the fi'le of this patent:

UNITED STETESPATENTS Date Number: Name reamed Seyfi'ertn June 119, 1928- 1,687,588 Pearson Oct; 16,. 1 -928 2,216,859: 

